The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device which can improve the operation characteristics of a semiconductor device.
In manufacturing a semiconductor device, metal lines are used to electrically connect elements to elements and lines to lines. As the semiconductor devices are more highly integrated, the widths and contact areas of metal lines decrease, and the resistances of the metal lines (including the contact resistance) increase. As the interval between a metal line and a contact plug becomes narrower, the parasitic capacitance induced by an insulation layer insulating the metal line increases.
Under this situation, various processing techniques for decreasing the resistance of a metal line and reducing the parasitic capacitance as mentioned above have been suggested. For example, attempts were made to use a low dielectric constant layer having a dielectric constant K not exceeding 2.9 that is lower than the 3.2 dielectric constant of a silicon oxide layer as the material of an insulation layer for filling the space between metal lines as the low dielectric constant layer also exhibits excellent gap-filling characteristics.
If a low dielectric constant layer is formed to fill the gap between metal lines, it may prevent the parasitic capacitance from being produced, which in turn may increase the operational speed of the semiconductor device and reduce the cross-talk between metal lines.
Hereafter, a conventional method for manufacturing a semiconductor device utilizing a low dielectric constant layer to fill the gap between metal lines will be briefly described.
An interlayer dielectric is formed on a semiconductor substrate, which is formed with a lower structure including transistors, to cover the lower structure. After depositing a metal layer on the interlayer dielectric, metal lines are formed by patterning the deposited metal layer.
A low dielectric constant layer is then deposited on the interlayer dielectric including the metal lines to cover the metal lines. The low dielectric constant layer is generally deposited in a spin-on type. The resultant substrate formed with the low dielectric constant layer is heat-treated in a furnace. A capping layer made of an oxide layer is formed on the low dielectric constant layer.
However, since the low dielectric constant layer has poor mechanical characteristics such as in strength and hardness, fails occur in the form of cracks appearing in the low dielectric constant layer or the low dielectric constant layer being lifted.
These fails can be prevented to some extent by implementing a heat treatment using ultraviolet (UV) rays and then forming a capping layer made of an oxide layer on the heat-treated low dielectric constant layer instead of performing a heat treatment in a furnace. Nevertheless, when implementing the heat treatment, the adhesive force of the low dielectric constant layer is reduced, by which the low dielectric constant layer can be lifted or the capping layer can be removed.
To cope with this problem, a method has been proposed, in which a heat treatment is implemented using ultraviolet rays after depositing the capping layer on the low dielectric constant layer. In this method, the adhesive force of the low dielectric constant layer can be increased since Si—O cross-linking is increased between the low dielectric constant layer and the capping layer.
However, in this case, C-based or H-based foreign substance contained in the low dielectric constant layer is outgassed, because the capping layer is deposited on the low dielectric constant layer having not undergone a heat treatment, and this leads to pollute the process chamber for depositing the capping layer, thereby causing poor deposition of the capping layer.
As a consequence, an additional cleaning process for removing the foreign substance in the process chamber is needed, by which time and cost for manufacturing a semiconductor device are increased, and a manufacturing yield is decreased.